The objective of this proposal is to develop ultra-sensitive ELISA (Enzyme-Linked ImmunoSorbent Assay) methods for quantification of HIV p24 antigen. At present, the p24 antigen test is relatively insensitive, being able to detect only 5- 10 pg/ml. This quantity of antigen may not be present in the serum of infected individuals, even when the virus is actively replicating. In fact, only about 50-60% of AIDS patients, 30-40% of ARC patients, and 10% of asymptomatic patients will have p24 antigenemia that is detectable. Therefore, the development of more sensitive p24 antigen tests is of great importance. It is in this context that we are proposing to develop a highly sensitive p24 antigen assays that will be less expensive than RNA viral load tests and appropriate for use both in developed and developing countries in which the limitations of infrastructure and laboratory capability prohibit nucleic acid testing. The specific aims of the Phase I and Phase II, in part, include 1) analyzing and optimizing of all variables affecting the accuracy and functionality of the p24 tests; and 2) validation of the HIV-1 p24 detection assay. Advantages of the proposed assays such as the increased sensitivity, signal-to- noise ratio, and dynamic range, reduced time and low cost of the analysis substantiates our belief that the proposed amplification method has a prominent commercial and scientific potential. PUBLIC HEALTH RELEVANCE: The development of the proposed method will allow using HIV p24 antigen tests for monitoring HIV infection, blood screening, identification of acute infection, to assist in the diagnosis of infection in the newborn, and in detecting antigen in supernatants from cultures. The performance of the developed tests will be improved significantly as compared with that for conventional assays. Successful completion of these studies will be beneficial for public health, and make available all of the technology needed for a substantial business opportunity to license the technology and manufacture commercial products.